#include <iostream>
using namespace std;

void CalcArea(const double* const ptrPi, const double*  const ptrRadius, double* const ptrArea)
{
	if (ptrPi && ptrRadius && ptrArea)
		*ptrArea = (*ptrPi) *  (*ptrRadius) * (*ptrRadius);
}

int main()
{
	const double Pi = 3.1416;
	
	cout << "Enter radius of circle: ";
	double radius = 0;
	cin >> radius;
	
	double area = 0;
	CalcArea(&Pi, &radius, &area);
	
	cout << "Area is = " << area << endl;
	
	return 0;
}